First results of the LEGEND-200 experiment in the search for $0\nu\beta\beta$

The LEGEND experiment is trying to find the extremely rare neutrinoless double beta decay of $^{76}$Ge using isotopically-enriched high-purity germanium (HPGe) detectors. The detection of this process would imply that the neutrino is a Majorana particle and the total lepton number would not be conserved, which could be related to the cosmological asymmetry between matter and antimatter through leptogenesis.

        

        The first phase, LEGEND-200, has been collecting physics data at LNGS in Italy for more than a year with 140 kg of HPGe detectors. The installation of more detectors is planned for the near future. The Collaboration has been focused on the analysis and understanding of the first set of LEGEND-200 data, the evaluation of the sensitivity and the study of the residual backgrounds.

        In this talk, the current observed background levels in the region of interest will be presented, the performance of the experiment in terms of background rejection and signal acceptance and a first model of the background composition before analysis cuts. Lastly, an update on the status of the future LEGEND-1000  phase will be provided.

        

        This work is supported by the U.S. DOE and the NSF, the LANL, ORNL and LBNL LDRD programs; the European ERC and Horizon programs; the German DFG, BMBF, and MPG; the Italian INFN; the Polish NCN and MNiSW; the Czech MEYS; the Slovak RDA; the Swiss SNF; the UK STFC; the Canadian NSERC and CFI; the LNGS and SURF facilities.